Infective mastitis due to bovine‐associated Streptococcus dysgalactiae contributes to clinical persistent presentation in a murine mastitis model

BACKGROUND: Mastitis caused by Streptococcus dysgalactiae (GCS) is a major pathology of dairy cows. The mechanisms by which GCS intramammary infection is established and maintained involve not only bacterial adherence and invasion but also modulation of the cytokines and TLR immune response. OBJECTIVES: The study aimed to evaluate characteristics of persistent infection of GCS collected from bovine mastitis milk in a murine mastitis model whose mammary structure is similar to that of dairy cows; dairy cow mastitis can be well simulated by using mice as models. HLJ2019 was tested for its ability to persistently infected mice by intramammary inoculation. METHODS: As antibiotics tested, establish an intramammary infection model in murine, histopathology analyses, relative expression of inflammatory cytokines mRNA and adherence and invasion in mMECs. RESULTS: It induced a robust inflammatory reaction in the mammary gland, characterized by histopathological changes, increased myeloperoxidase activity and induced expression of inflammatory cytokines (TNF‐α, IL‐6, IFN‐γ, IL‐10, IL‐1α and IL‐1β) and TLR2/4, the exhibited strong LDH release, adhesion and invasive abilities in contact with mMECs. CONCLUSION: These results contribute to increase the available information on host‐pathogen interaction and point out the need for further research to expand the knowledge about these interactions for developing new strategies to intervene in the intramammary persistent infection progress.